The present invention is related to the field of laser sources for fiberoptic networks and, more particularly, to lasing elements created in a doped optical fiber.
As the use of fiberoptic networks have become more prevalent in telecommunications, the number of fiberoptic light sources has rapidly increased. Semiconductor lasers are commonly used for these sources. WDM (Wavelength Division Multiplexed) networks, in particular, demand a large number of laser sources for signal generation. Since the wavelength of an optical signal is used to direct the signal from its source to its destination, each user typically has a laser source operating at a specific wavelength different from other laser sources. A stable laser source having a fixed output wavelength is very desirable. Furthermore, an emerging standard is Dense WDM proposed by the ITU, the International Telecommunications Union, in which the separation between communication channels is only 0.8 nm in wavelength, or 100 GHz in frequency. Thus light source(s) for such a network must also offer a precise selection of wavelengths and a very narrow output linewidth for each selected wavelength, i.e., the wavelength of the output signal must be concentrated in a very narrow portion of the optical spectrum.
New types of laser source are fiber lasers which may be a Distributed Bragg Reflector (DBR) fiber laser or a Distributed Feedback (DFB) fiber laser. In each fiber laser source a rare-earth element doped optical fiber section is coupled to one or more fiber Bragg gratings so as to lase at one or more selected output wavelengths. In a fiber laser source, a pumping laser supplies the energy at one wavelength and the laser source generates an output at a different wavelength. Nonetheless, this laser source has a relatively low output power and the advantages of this laser source has yet to be appreciated in the fiberoptics industry.
The present invention presents arrangements of DBR and DFB fiber lasers by which light output at different and specific wavelengths are generated on an optical fiber. The linewidths around these specific wavelengths are very narrow with excellent wavelength selectivity. The arrangements are miniaturized for easy installation in a fiber optic network and for stable maintenance of the laser output power and wavelength over time and changes in ambient temperature.